PROJECT SUMMARY Many cognitive and affective functions are preserved during aging and it has been suggested that older people are better at regulating negative emotions. Previous studies have elucidated regional brain activations in response to social emotional stimuli. However, the neural circuits regulating physiological responses to social emotions and how these processes differ between young and old people have not been explored. Emotion is represented in complex interactions between frontal limbic areas and subcortical circuits that embody physiological reactions. Emotional, compared to non-emotional, stimuli elicit robust autonomic responses congruent with interoceptive perception. Negative emotions are associated with decreased heart rate variability (HRV) and increased skin conductance level (SCL); in contrast, positive emotions are associated with increased HRV and decreased SCL. On the other hand, less is known about how cerebral activations to emotional stimuli in a social context are related to autonomic responses. No studies have examined the causal relationship between cerebral activities and autonomic responses to social emotional stimulation or the effects of aging on these regulatory activities. This R21 application aims to address these gaps of research. We will assess and recruit young and old adults to participate in brain imaging while exposed to social emotions. We will examine (a) whether and how social, compared to neutral, emotion scenarios, evoke changes in HRV and SCL, and how these changes vary between young and old individuals; and (b) how regional responses to social emotions correlate with and Granger cause HRV and SCL, building on our work of Granger causality analysis, and how these regulatory activities vary between young and old individuals. We will also explore how autonomic responses, regional activations to social emotional stimulation and their regulation of autonomic responses relate to social anxiety as well as age and gender effects on the relations. Together, the study will elucidate cerebral responses to social emotions, how regional and circuit activities regulate physiological responses to social emotions, and the influence of aging on these neural regulatory activities. The potential findings may advance our knowledge of the effects of aging on emotional experience and move aging and affective neuroscience research in new directions.